Mechanical formation of micro- and nano-plastic materials for environmental studies in agricultural ecosystems.

Autor: Astner AF; The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America., Hayes DG; The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America. Electronic address: dhayes1@utk.edu., O'Neill H; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Evans BR; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Pingali SV; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Urban VS; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Young TM; The University of Tennessee, Center for Renewable Carbon, 2506 Jacob Dr, Knoxville, TN 37996, United States of America.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2019 Oct 01; Vol. 685, pp. 1097-1106. Date of Electronic Publication: 2019 Jun 17.
DOI: 10.1016/j.scitotenv.2019.06.241
Abstrakt: Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There exists a need for more representative materials in fundamental studies of the fate, transport, and ecotoxicity of MPs and NPs in soil ecosystems. The objective of this study was therefore to develop a procedure to produce MPs and NPs from agricultural plastics (a mulch film prepared biodegradable polymer polybutyrate adipate-co-terephthalate (PBAT) and low-density PE [LDPE]), and to characterize the resultant materials. Soaking of PBAT films under cryogenic conditions promoted embrittlement, similar to what occurs through environmental weathering. LDPE and cryogenically-treated PBAT underwent mechanical milling followed by sieve fractionation into MP fractions of 840 μm, 250 μm, 106 μm, and 45 μm. The 106 μm fraction was subjected to wet grinding to produce NPs of average particle size 366.0 nm and 389.4 nm for PBAT and LDPE, respectively. A two-parameter Weibull model described the MPs' particle size distributions, while NPs possessed bimodal distributions. Size reduction did not produce any changes in the chemical properties of the plastics, except for slight depolymerization and an increase of crystallinity resulting from cryogenic treatment. This study suggests that MPs form from cutting and high-impact mechanical degradation as would occur during the tillage into soil, and that NPs form from the MP fragments in regions of relative weakness that possess lower molecular weight polymers and crystallinity.
(Copyright © 2019 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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